Bead rollers are used in techniques for sheet metal shaping to achieve stiffening of sheets, to model a sheet metal to a desired structure or to design a sheet as desired. The stiffening or the design is accomplished by providing the sheet with profiles, such as beads in the form of notches, steps or ridges, which may be linear or curved as desired, along the sheet.
In the automotive industry there are a lot of sheet details which may have to be shaped into different designs. With regard to types of vehicles manufactured in series it is obvious to use pressing tools which model sheet details for a specific type of vehicle in a press, where sheets aimed for a specific location in the vehicle are stamped in a desired amount having identical designs or patterns. On the other hand, if vehicles like cars or motor bikes are manufactured in solitary numbers, it would be too costly to utilize a number of different presses to model different sheet details, for example details of the coach of a car, fenders of a motor bike, etc. In cases like that, where solitary details are to be shaped of sheets to constitute, for example, fenders, sides of doors, bonnets, lids or other details of a vehicle, a bead roller can be used to model the sheet to the stiffness, structure and design desired.
Bead rollers are known since long. Examples of such machines are disclosed in Published European Patent Application EP1518616 A2 and U.S. Pat. No. 6,591,651, both of which are incorporated herein by reference. The function of a known bead roller, exemplified by said documents is described in the following with reference to FIGS. 1, 2a and 2b. 
FIG. 1 depicts a conventional Prior Art bead roller. Machine 101 is, in this case a model mounted to the floor by means of a floor stand 102. Further, machine 101 comprises two drive shafts 103 and 104 (FIGS. 2a, 2b) mounted in parallel. The ends of shafts 103 and 104 are adapted to receive different types of dies 105a, 105b (shown in FIGS. 2a, 2b) depending on the type of bead desired, on a sheet being fed between dies 105a, 105b. Drive shafts 103, 104 are journaled in bearings in respective arms 106, 107 and have their inner ends connected to respective gear wheels and transmission to a motor 108 for driving shafts 103 and 104. Arms 106, 107 are fixed to floor stand 102, usually in such a way that drive shafts 103 and 104 are parallel to the ground on which floor stand 102 is mounted. The drive of the shafts 103 and 104 is arranged so that the dies counter rotate and thereby feed a sheet plate contacting dies 105a, 105b from the upper and lower side, respectively, in a forward direction (normally away from an operator). On the upper arm 106, in this example, a screw 109 is mounted. By means of this screw 109, a desired pressure between dies 105a, 105b can be set.
Operation of the prior art bead roller is illustrated in FIGS. 2a and 2b. In these Figures, being principal outlines, drive shafts 103 and 104 and their mountings in bearings in the arms 106, 107 are shown more in detail. A sheet 110 and an ongoing shaping of sheet 110 are also visible. FIGS. 2a and 2b depict how a bead, in this case being a ridge along the sheet, is accomplished. For this purpose a first die 105a and a second die 105b are mounted on the outer end of the respective drive shafts 103, 104. The first die 105a is furnished with a circumferentially running sunk recess 111a, while the second die 105b is furnished with a circumferentially running ridge 111b corresponding to and matching the curvature of said recess 111a. As dies 105a, 105b are counter rotating with respect to each other when driven by shafts 103, 104, sheet 110 will be fed forward between dies 105a, 105b with a pressure is set as desired, whereby a bead will be shaped, in this case as a bead designed as a ridge extending a desired length across the sheet 110. By manually steering the sheet in different directions during the operation in a plane substantially tangentially with the two dies 105a, 105b, a desired curvature of the bead can be accomplished. The cross sectional profile of the bead is determined by the choice of the two matching dies 105a, 105b. 
With reference to FIG. 3, it is illustrated how difficulties can occur during the described sheet working according to Prior Art. A simple embodiment of a bead roller according to conventional technology is depicted schematically, simplified and stereotyped in FIG. 3. According to FIG. 3, a bead, in this case a ridge elevated from the sheet surface along a curve in the middle of the exterior surface of a fender 110 of a motorbike is under preparation. As clearly disclosed by the figure it will be impracticable to achieve the desired bead in this case, as the restricted space between the two drive shafts 103, 104 prevents the introduction of one of the lengthwise edges 113 of the fender between the drive shafts 103, 104 of the machine due to the heavy bend in the fender cross section. FIG. 3 illustrates how the edges of the fender intersect deeply into the area 113, which needs to be freely available to carry out the described operation. In the case exemplified, drive shaft 104, and of course also a housing, for example the housing of an arm 106, surrounding drive shaft 104, block the desired actions on the maneuvering of the fender.